fw_cfg: add etc/msr_feature_control

The file already existed, but nobody had noticed the warning until now.
Add it at the bottom, since that is where unknown files go in legacy mode.

Fixes: 217f1b4a72 ("target-i386: Publish advised value of MSR_IA32_FEATURE_CONTROL via fw_cfg")
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

hw/nvram/fw_cfg.c

@@ -878,6 +878,7 @@ static struct {
     { "etc/tpm/log", 150 },
     { "etc/acpi/rsdp", 160 },
     { "bootorder", 170 },
+    { "etc/msr_feature_control", 180 },
 
 #define FW_CFG_ORDER_OVERRIDE_LAST 200
 };